This might sound silly, but my best screens came from a Michaels crafts store. They were selling at 50 cents for square foot pieces and I easily cut the plastic screens down to my desired size. They were actually an embroidery matrix that is used for that or needlepoint,- I don't know their actual marketed function, but they excelled as my screens; however the mesh size is only good for flies and mosquitos and not for gnats. 'take care and joy, Aythya crew